The gap seems almost irreducible because among other things, as John Curtice has said, it’s about the economy, stupid. Being the bird in the bush, it’s the Yes camp that has run into the greater credibility problem in that regard. That gives you some measure of the difficulty of selling an unknown to the middle class.

And the so-called Project Fear has plenty of intangibles to work off…

…just 17% say they would personally be better off as a result of independence, down two points on both March and December. As many as 43% believe they would be worse off.

My prediction from that time that the outcome of the #IndyRef is all but decided may yet prove an embarrassing hostage to fortune, but I suspect that despite all the stormy squalls it is the No campaign which is more in tune with the current unpredictable climate by seeming to offer less risk.

In his column for the FT this week, Janan Ganesh writes about the similarly negative strength of Cameron’s hand in any upcoming Brixit referendum:

Britons will not base their vote on a forensic reading of the powers lost and gained by Mr Cameron. Instead, they will weigh up the (relative) clarity of membership with the ambiguity of exit.

The Out campaigners can only win if they clear up exactly what “Out” means: whether leaving the EU entirely; or settling for a Swiss-style middle option; or inventing a third model of membership that offers access to the internal market without the concomitant regulations.

“Trust us, it will all work itself out” is a brave line to use on an electorate as risk averse as the British.

Of course, that does not mean that an upset is not possible. But the Irish experience suggests that in order to get positive proposition which displaces the status quo you have need to have a lead of sufficient size to withstand the change sentiment that usually kicks in towards the poll date.

The big problem for the Yes camp is that it has yet to hit the front. Even the scrupulously small ‘c’ conservative analysis of John Curtice is now suggesting that it’s a big ask for Salmond…

It is going to be very, very difficult. It has looked difficult for quite a while. It needs a game changer, and where is that going to come from during the course of the summer?”

According to Quintin’s Ten Iron Laws for winning a referendum, Alex Salmond has done most things well. Two things may help defeat him in June: one, the lateness of the date in his own government’s lifetime; and two, the messiness around the economic forecasting has helped unravel the appealing simplicity of the social union.

Perhaps more relevantly though, this particular solution to the West Lothian seems to have an imprecise ceiling at around 40%+ of the Scottish population. At the end of the day the experience may help harden the perceptions of a separate and serious Scottish political culture.

And one that London-headquartered parties will continue to take for granted only at their own and the Union’s peril.